Use of lead salts of nitroamino guanidine as initiating charge in firing devices



1943- LE ROY v. CLARK 2,326,008

USE OF LEAD SALTS 0F NITROAMINO GUANIDINE AS INITIATING CH E FOR FIRING DEVICES Filed v. 1940 INVENTOR. LE/F'OY 1/. 0142/1,

yet the invention is Patented Aug. 3, '1943 USE OF LEAD SALTS or NITROAMINO GUANIDINE AS INITIATING CHARGE IN FIRING DEVICES Le Roy V. Clark, Latrobe, Pa., assignor to American Cyanamid & Chemical Corporation, NEw York. .N. Y., a corporation of Delaware Application November 1, 1940, Serial No. 363,815

12 Claims.

This invention relates to an improved firing device and more particularly to an improved blasting cap of the type containing a base charge and an initiating charge.

It is well known that .the commercial firing devices used by the art may be either closed shell electric blasting caps of either the delay or instantaneous type or open shell fuse blasting caps. The base charge-initiating charge combination of the present invention may be used with any or all of the above types of caps with equal success.

The primary object of the invention is to provide an improved base charge-initiating charge combination for such firing devices. A further object is to provide a blasting cap with a base charge and having an initiating charge which is less sensitive to friction and impact than the previous initiating charges used by the art. A still further object of th invention is to provide a firingdevice of the above type in which a lead salt of nitroaminoguanidine is included in the initiating charge.

LNAG either alone or in admixture with oxidizing salts. This. charge is subjected to any convenient pressure and may or may not be topped by an ignition composition as desired.

Figure 2 shows an electric blasting cap in which the base charge comprises 0.25 gram of PETN pressed at 3,000 pounds pressure per square inch, and in which a loose initiating charge 2 comprises 0.40 gram of a mixture of LNAG and potassium chlorate in substantially proportions of 80 to 20. As is usual these caps are provided with a cast plug 3 carrying a pair of lead wires the ends of which are bridged as at 5. A waterproof compound 8 may then be poured into the shell on top of the plug 3, and the combination topped off withv a sealing compound I. When the above combination is contained within a .25 calibre shell; this cap contains-sufficient explosive material to be classed as a No. 6 cap according to the United States Bureau of Mines Standard.

Similarly the bas charge LNAG combination may be used in the delay electric blasting cap of above of pentaerythr tol tetranitrate (hereinafter referred to for, convenience as PETN) as a base charge. It is to be understood that the-invention contemplates the use of such combinations in any type of firing devices.

The invention further contemplates the novel combinations hereinafter described and shown in the accompanying drawing, in which- Fig. 1 is a sectional view of a fuse blasting cap; 2 is a similar view of an electric blasting ap; and

Fig. .3 is a similar view of a delay electric blasting cap.

All of the above caps embody the present invention.

Referring now to the simplest form of the invention which is that with relation to a fuse cap of the .22 calibre open shell type shown in Figure 1, a base charge is shown at l of any suitable material. This may be tetranitromethyl analine, nitro starch, trinitrotoluene, picric acid or any of theusual non-initiating substances commonly used in the art. While we prefer to use PEI'N, ot to be limited thereto.

Fig. 3. Here a delayv element 8 is superimposed upon the initiating charge 2 and contains the usual delay powder train. In this case, the plug I, which carries the lead wires 4, is provided with a paste type ignition composition l0 in, which the bridge wire 5 is embedded. The inner casing is provided with a, vent ll communicating with a gas chamber l2. This permits escape of generated or expanding gas within the casing during burning of the fuse and prevents premature rupture. The waterproof fill 8 and sealing material I are used here as is true in. the ordinary electric blasting cap. 3 r

The caps prepared in accordance with the above examples were tested by the standard sand test and lead'plate tests used by the art and were found to be equivalent'to the various N9. 6 caps now available on the market in perform ance. As a matter of fact, they gave a better sand test than afulminate-tetryl No. 6 cap and a better. lead plate test than a diazodinitrophenol-tetryl combination or a fulminate-tetryi combination cap.

In accordance with this invetnion, the initiating charges of. the specific examples given here-- for a PEI'N or other base charge or it may be used in suitable admixture with an oxidizing The initiatingchars shown'at 2 comprises as agent.

It will also be understood that by varying the weight of the base charge dependent upon the specific material used, the caps described can be manufactured to conform to any of the standard strengths that may be desired. Further as will be obvious to those skilled in the art, the quantities of explosives used as the base charge and initiating charge for the specific examples given compare very favorably to the quantities of explosives used in most of th commercial caps of the art. As a matter 'of fact, the quantities here used are less.

In the preparation of the above examples there were definite advantages derived from the use' of LNAG as the initiating charge for the base charge over the use of mercury fulminate or lead azide. This relative insensitiveness is shown by the following table:

TABLE I Using the United States Bureau oi Mines Friction Pendulum' Type B.

Another very important advantage in the use of LNAG is due to its lack of sensitivity to impact as is shown in the following table:

TABLE II Sensitivity to impact Maximum height of drop Explosive oi gm.

weight for no explosion Cms. Lead nitroaminoguanidinenn 27. Diazodinitrophenol 22. 5 Lead azide l7. 5 Mercury iulminate l5. 0

1 Using United States Bureau of Mines Small Impact Machine.

It is apparent from the results in the above tables that blasting caps containing LNAG as an initiating charge superimposed upon a base charge and particularly one containing PETN, are much safer to manufacture and handle than the initiating charge-base charge combination caps known to the art. Such an increase of safety in operation constitutes a major improvement in the explosive art.

The fuse blasting caps prepared show further advantages and improvements over the blasting caps of the art in that when LNAG is used as the initiator, a. confining capsule is not required. Where mercury fulminate is used as an initiating charge, it must be confined with a. capsule as otherwise there is not suflicient explosive force to properly detonate the base charge, particularlywhere the latter is PETN. It is also to be noted that the-use of lead azide in open copper shelisis not recommended because copper azides will be formed which are very sensitive and dangerous to handle. Lead azide is further relatively diflicuit to ignite by the spit of a safety fuse and for this reason, if this substance is used in blasting caps, it is customary to place an 1:-

nition charge over the initiating charge'in order to insure ignition. This is objectionable from the standpoint of economy and efficiency.

While it is possible to use mercury fulminate in open shell caps having a PETN base charge, it is necessary to reinforce the fulminate with a capsule to insure positive detonation of the base charge and whenever a capsule is thus used, it is advisable to place an ignition or wafer charge above the capsule to insure ignition of the initiating charge by the spit of the fuse. Here again such a device shows disadvantages from the standpoint of economy and efficiency when compared to the devices of this invention using INAG as an initiating charge.

The use of LNAG is, therefore, highly advantageous and provides the art with an improved firing device from the standpoint of safety, economy and efliciency of manufacture, positiveness of detonation and'simplicity of construction.

A lead salt of nitroaminoguanidine may be conveniently prepared as follows:

9 parts by weight of nitroaminoguanidine are dissolved in 300 parts of water at 83 C. 9 parts of pure precipitated lead hydroxide are then added to the solution and rapidly agitated for 15 minutes at from to 80 C. Upon cooling to 15 C., yellow prismatic crystals form which may be filtered, washed with alcohol and dried at 35' C.

While the invention has been shown and described with particular reference to specific embodiments, it is to be understood that it is not to be limited thereto but is to be construed broadly and restricted solely by the scope of the appended claims.

I claim:

1. A firing device containing a base charge of pentaerythritoI tetranitrate and an initiating charge of lead nitroaminoguanidine superimposed thereon.

2. A firing device containing a base charge of pentaerythritol tetranitrate, and an initiating charge superimposed thereon which comprises an admixture of lead nitroaminoguanidine, and an oxidizing agent.

3. An electric blasting cap'containing a base charge of pentaerythritol tetranitrate, and an initiating charge of lead nitroaminoguanidine J charge superimposed thereon which comprises an admixture of lead nitroaminoguanidine, and an oxidizing agent.

'7. A firing device including a base charge of pentaerythritol tetranitrate and an unconfined initiating charge of lead nitroaminoguanidine superimposed thereon.

8. A firing device containing a. base charge of pentaerythritol tetranitrate and an initiating charge superimposed thereon which comprises an admixture of lead nitroaminoguanidine and potassium chlorate.

9. A firing device including a base charge of pentaerythritol tetranitrate and an unconfined initiating charge superimposed thereon which comprises an admixture of lead nitroaminoguanidine and an oxidizing agent.

10. An electric blasting cap containing a base charge of pentaerythritol tetranitrate and an initiating charge superimposed thereon which comprises an admixture of lead nitroaminoguanidine about 80% and potassium chlorate about 20%.

11. A fuse blasting cap containing a base charge 10 of pentaerythritol tetranitrate and an initiating charge superimposed thereon which comprises an admixture of lead nitroaminoguanidine about 80% and potassium chlorate, about 20%.

12. A firing device containing a base charge of pentaerythritol tetranitrate and an unconfined initiating charge superimposed thereon which comprises an admixture of lead nitroaminoguanidine and potassium chlorate.v

LE ROY V. CLARK. 

